A DEADLY cargo of radioactive nuclear waste sat in a railway siding for hours, surrounded by houses and less than 100 metres from a school.

Exposure for just 30 seconds to the radioactive material inside the load of spent fuel rods would mean certain death.

Amazingly, the material - which could be used to make dirty bombs - was left on a flatbed rail carriage for hours before it was transported to the Sellafield reprocessing plant in Cumbria.

Locals, including children, were able to walk unchallenged to within feet of it.

A flimsy wire-mesh fence is all that stood in their way. Terrorists could easily have jumped the fence to blow up or steal the lethal freight. The fall-out would contaminate a huge area, making it uninhabitable for hundreds of years. Bosses at nuclear train operators Direct Rail last night vowed to tighten security after The Sunday Mirror told them about the lapse.

We were also able to work out the train's route on its 300-mile journey from Bridgwater in Somerset to Sellafield - from material freely available over the counter and on the internet.

Dr John Large, Britain's top independent nuclear expert, said: "Every one of these trains would be a potential target for terrorists.

"The flasks of fuel rods could be easily penetrated by a rocket-propelled grenade. If a flask was penetrated it would cause radiation over a wide area.

"The contents are intensely radioactive. Exposure for just 30 seconds would mean death."

We were alerted to the shocking security lapse by worried residents after we revealed two weeks ago that July's London suicide bombers were planning to hit a nuclear target.

We had also exposed another blunder that allowed us to walk within feet of the huge nuclear reactor at the Dounreay reprocessing plant in Scotland.

In this new scare, radioactive waste from the Hinckley Point nuclear power station in Somerset is regularly left at the rail sidings in Bridgwater 15 miles away after being transported by road. The sidings are in the middle of rows of terrace houses, just a few metres from people's front doors.

One horrified mum even took pictures of children playing on the fence right above the concrete flask containing the nuclear waste.

She said: "These kids were climbing all over the fence and walking right up to the flask."

Another worried mum, Terri Glassup, 22, spoke out as she pointed to the trailer from her front door: "As a parent I am worried sick about this hazardous waste on our doorstep. God only knows what would happen if someone decides to blow it up."

Irene Hodge, 70, said: "I have lived here all my life, but I hate it now. I shudder to think what would happen if the waste leaked or was targeted in any way. There are thousands of people living nearby who would be wiped out."

The deadly nuclear material was left at the sidings for hours before a train finally arrived to transport the cargo the 400 miles to Sellafield.

From trainspotting magazines, bought over the counter, and the internet, the Sunday Mirror was able to establish the exact routes and times of the trains. Our investigators were able to locate the marshalling yards in the Midlands where the cargo joined similar trains from power stations all over the South. Last night anti-nuclear train campaigner Martin Forwood said: "I have been sounding clear warnings about these trains for years.

"These highly radioactive convoys travel through our towns and cities every week. It is easy to find out about their movement and times."

Direct Rail Services' commercial director Chris Connelly said: "We have been made aware of the potential for people to gain access to our rail compound at Bridgwater.

"Whilst this compound is used to transfer flasks from Hinckley power station, this activity is only ever undertaken whilst security and other personnel are in attendance. Fuel flasks are never left unattended in the compound."